The present invention relates to a sole plate for an electric iron adapted to be fixed to a heating body and whose pressing surface comprises a coating improving the sliding of the iron on the material to be ironed.
The prior art teaches the provision of many such coatings, thus reflecting the constant care for seeking a material with a very low coefficient of friction to iron all cloth. By way of example can be cited the following coatings: polytetrafluorethylene, enamel, ceramic, stainless steel, chromium, etc.
The applicant has particularly used for a number of years in pressing irons known as OPTIMATE, ULTIMATE, a coating comprising a layer of brilliant nickel covered with a deposit of chromium. Such a coating is known to offer for the most part a high coefficient of sliding over most cloth, as well as an outstanding appearance thanks to its extremely smooth and brilliant surface. However, this smooth surface is not ideal and has, not only a sensitivity to cracking due to mechanical shocks either during production or during improper use, but also a friction which is too high, on synthetic fabric such as polyesters.
The object of the present invention is therefore to overcome the drawbacks mentioned above by providing particularly a coating that will be practically universal for pressing of all cloth by improving substantially the sliding on polyesters.
According to the invention, the coating comprises an underlayer of satin-finished nickel, and a surface layer of chromium.
According to the applicant, the particular advantage of this coating is due to the typography of its external surface, which has a parameter of rugosity Ra substantially greater than that obtained with a brilliant nickel coating and which is of a ratio at least equal to 30.
Tests carried out by the applicant convincingly prove that the sliding of the sole plate is inversely proportional to the parameter Ra. Micrographic analyses of the typography of the coating show clearly that it has a myriad microcavities, which by interaction with the steam generated during pressing, give rise to an astounding improvement in sliding of the sole plate over all cloth, and particularly polyesters.